1. Field of the Invention
The present invention generally relates to a servo pattern deviation correcting method and a disk apparatus using the same. More particularly, the present invention relates to a servo pattern deviation correcting method which corrects the positioning of a read/write head even when deviation of a servo pattern from the position of a target track of a disk occurs, and to a disk apparatus which uses the servo pattern deviation correcting method.
2. Description of the Related Art
In a conventional disk apparatus, a servo pattern is written to a disk through a servo track writing (STW) or the like. When data is read from or written to a target track of a disk, the head is placed at the right position on the track in accordance with position information obtained from the servo pattern recorded in the disk. However, the actual track that is actually produced by the head during the rotation of the disk (hereinafter, called the trace of the head) is likely to deviate from the position of the target track due to repeatable run-out caused by the oscillation of the head during the servo track writing.
For example, FIG. 1 shows a positional relationship between the trace of the head and the target track of the disk in a certain situation. As indicated by the solid line in FIG. 1, the servo pattern 21 is written to the disk along the target track 23 (indicated by the dotted line) at positions that are irregularly separated from the target track 23. FIG. 2 shows a positional relationship between the trace of the head and the target track of the disk in another situation. As indicated by the solid line in FIG. 2, the starting position of the servo pattern 22 at the start of the writing significantly deviates from the end position of the servo pattern 22 at the end of the writing.
As described above, the head is positioned to the target track in accordance with the position information obtained from the servo pattern of the disk. When such servo pattern deviation occurs, it is difficult for the conventional disk apparatus to accurately place the head to the right position on the track.